The roles of cyclic nucleotides and protein kinase in normal vision and in retinal degeneration have been further examined: 1. A direct gene-dose relationship has been found between the rds (retinal degeneration slow) gene and cyclic GMP phosphodiesterase activity in mutant mice. 2. Cyclic AMP-dependent protein kinase has been characterized in fetal and adult retina and in cultured human retinoblastoma cells. 3. Vanadate has been found to stimulate phosphotyrosine phosphorylation in quiescent Nakano lens cells but to not directly stimulate DNA synthesis by itself. 4. An in vivo system for studying calcium phospholipid-dependent protein kinase (C-kinase) has been established using the rat as a model. 5. A specific cyclic GMP phosphodiesterase of the retinal interphotoreceptor matrix has been found that is distinctly different from the light-activated, enzyme found in the retinal photoreceptor.